The present disclosure relates to a solid-state image pickup device and an electronic apparatus that are capable of preventing leakage of charges between adjacent pixels. A plurality of pixels perform photoelectric conversion on light incident from a back surface via different on-chip lenses for each pixel. A pixel separation wall is formed between pixels adjacent to each other, and includes a front-side trench formed from a front surface and a backside trench formed from the back surface. A wiring layer is provided on the front surface. The present disclosure is applicable to, for example, a backside illuminated CMOS image sensor.